Epitaxial growth of inorganic materials onto other inorganic substrates is an extremely important field of modern materials science which involves the nucleating and growing of atoms and molecules into highly structured lattices on top of other crystalline lattices. The most important and commonly used means to form thin layers of certain crystalline materials is by growth from the vapor phase (for more on epitaxy and vapor phase see "Recent Developments in the Theory of Epitaxy," J.H. van der Merwe, in Chemistry and Physics of Solid Surfaces V, Eds. R. Vanselow and R. Howe, Springer-verlag, N.Y. (1984), p. 365-401, and "Growth from the Vapor Phase," in Modern Theory of Crystal Growth I, Ed. A. A. Chernov, Springer-Verlag, N.Y. 1983, Chpt. 8.
Epitaxial growth of large anisotropic organic molecules on inorganic substrates is also known. Vapor deposited phthalocyanine thin layers deposited onto graphite, alkali halide, and muscovite single crystals are reported (see N. Uyeda, T. Kobayashi, E. Suito, Y. Harada and M. Watanabe, J. Appl. Phys. 43(12) (1972) 5181; M. Ashida, Bulletin of the Chemical Society of Japan 39(12), (1966) 2625-2631 and 2632-2638; H. Saijo, T. Kobayashi and N. Uyeda, J. of Crystal Growth 40 (1977) 118-124; M. Ashida, N. Uyeda and E. Suito, J. of Crystal Growth 8 (1971) 45-56; Y. Murata, J. R. Fryer and T. Baird, J. of Microscopy, 108(3) (1976) 261-275; J. R. Fryer, Acta Cryst. A35 (1979) 327-332; M. Ashida, N. Uyeda and E. Suito, Bulletin of the Chemical Society of Japan 39(12) (1966) 2616-2624; Y. Saito and M. Shiojiri, J. of Crystal Growth 67 (1984) 91; and Y. Saito, Applications of Surf. Sci. 22/23(1985) 574-581.
Epitaxial growth and polymerization of synthetic and biopolymers onto alkali-halide substrates, from solution, melt, and vapor phases is also known. Recently described is the use of inorganic minerals as substrates to control the vapor transport and solution growth habits of protein crystals (see A. Mcpherson and P. J. Schlichto, J. Cryst. Growth 85 (1988) 206). U.S. Pat. No. 4,016,331 discloses epitaxially growing, by vapor phase methods, thin organic layers onto substrates of thin sheets or webs of thermoplastic polymeric materials which have been made highly oriented in the plane of the sheet by stretching and heating or mechanical rubbing in one direction.
Shortcomings of inorganic single crystals as substrates for epitaxial growth are many. For example, the number and types of single crystals for proper registry for coating is limited; the crystal surface may be reactive, oxide coated, and/or contain adsorbed water molecules; the substrate may be opaque to light, have undesirable electronic and/or thermal properties and the like.
Many of the shortcomings of inorganic single crystals as epitaxial substrates apply as well to those of stretched and/or heated organic web substrates, which, by their nature, induce a fiber like anisotropy in the plane of the film that may be undesirable (see U.S. Pat. No. 4,016,331).